This project represents a continuation of previous work directed at the elicitation of biologic principles governing normal tissue and tumor responses to combined modality (drug-radiation) tumor therapies. Normal tissue studied include the gastrointestinal mucosa and bone marrow (hematopoiesis). Tumor systems used include the P815X2 mastocytoma, T1699 mammary carcinoma, Lewis lung carcinoma and the H4IIE2 hepatoma. End points for acute tissue responses include cell kill (in vivo and in vitro clonal assays), proliferative indices (3H-TdR incorporation, labeling studies, G.F. determinations, etc.), and the fate of lethally damaged cells (3H-IUdR studies). Comparative studies relative to the differing responses of tumors grown as solid, metastatic, or, in certain instances, as ascites tumors and in vitro modes are an integral part of the program. Also, other normal tissue end points relative to toxicity and functional activity are utilized in modeling acceptable treatment configurations. The overall project goal continues to be the evolution of treatment-associated concepts that will result in the greatest amount of tumor control consistent with minimal attendant normal tissue toxicity.